Web packaging

ABSTRACT

Plastic webs and films are heated to an elastomeric state, pressed while warm between a pair of crush rolls, and wound tightly around one of the crush rolls. Packages of the plastic webs and films prepared in this way are dense and free from air pockets.

United States Patent 71,599 12/1867 Frink Edward Sroka Newton, Mass.

Apr. 3, 1969 Aug. 31, 1971 Tenneco Chemicals, Inc.

lnventor Appl. No? Filed Patented Asslgnee WEB PACKAGING 6 Claims, 2Drawing Figs.

U.S. Cl 242/55, 38/49, 242/65 Int. Cl B65h 75/00 Field of Search 242/55,55.01, 56, 561, 56.2, 64, 65, 66, 67.1, 672, 67.5; 38/44, 49, 52, 53;18/10; 264/288, 289

References Cited UNITED STATES PATENTS 7 dense and free from airpockets.

2,232,223 2/1941 Gardner 38/52 X 2,526,318 10/1950 Battin 18/10 X3.224.698 l2/l965 Conti 242/55 3,279,718 10/1966 Arterton et a1. 242/6713,357,651 12/1967 Robinson 242/65 3,433,429 3/1969 Schnitzspahn 242/653,458,617 7/1969 lsley et a1 264/289 X Primary Examiner-Stanley M.Gilreath Assistant Examin2rWerner H. Schroeder Attorneys-Daniel J.Reardon, Saul R. Bresch, George E. Lilly and Evelyn Berlow ABSTRACT:Plastic webs and films are heated to an elastomeric state, pressed whilewarm between a pair of crush rolls, and wound tightly around one of thecrush rolls. Packages of the plastic webs and films prepared in this wayare PATENTED M1931 IHYI INVENTOR. {DA/4E0 4. Geo/ 4 WEB PACKAGING Thisinvention relates to the packaging of webs and films. More particularlyit concerns novel arrangements for winding webs and films aboutcylindrical cores without entrapment of air bubbles.

In packaging many types of plastic sheet material, for example, films ofpolyvinyl chloride, the material is wound about cylindrical cores sothat it can be easily stored and shipped. Materials of this nature,however, tend to experience surface irregularities in the nature ofprotrusions and indentations. As a result, when the material is woundabout a core during packaging, these surface irregularities entrap airbetween the successive layers being wound. This situation results in apackaged product which is unduly bulky and which degrades the appearanceof the film or sheet material. In addition wrinkles or creases mayresult as successive layers are tightly wound about each surfaceirregularity.

A film of polyvinyl chloride which is free from surface irregularitieswill on the other hand when tightly wound about a core provide a deepbluish appearance free from blemishes. The package will have a highdensity and will also provide a high quality appearance.

These desirable characteristics have been quite difficult to achieve.Attempts have been made to eliminate surface indentations andprotrusions during winding by subjecting the film to tension while it isbeing wound. In most cases, however, this merely stretched the filmthereby causing variations in thickness or caliper as well as in width.In the case of thin films especially any such decrease in thickness orcaliper is unac ceptable, for the film will tear or rupture. Attemptshave also been made to eliminate surface irregularities by softening thematerial and reforming it through plastic deformation. Thesearrangements also have proved expensive, difficult to control, andgenerally unacceptable.

The present invention overcomes the above described difficulties of theprior art and permits tight winding of many plastic sheet materialsabout cores without air entrapment and without the air pockets,blemishes and other appearance-affecting characteristics which resultfrom surface irregularities. Moreover the present invention accomplishesthese results without the changes in thickness and width which resultfrom known tension and stretching techniques.

The present invention is based in part on the recognition that forcesmay be applied to sheet material in a manner to flatten surfaceirregularities without affecting the overall character of the sheet solong as those forces are confined to the elastomeric deformationproperties of the sheet material. According to the present invention,the sheet material is raised to a temperature at which it exhibitssubstantial elastomeric properties. Then, while the material is in thisrange, it is subjected to a high pressure ironing action produced by thenip of a pair of squeeze rolls. At the same time the material is woundtightly about one of the rolls. The squeeze rolls press down uniformlyon the sheet. However in the region of each surface irregularity thematerial will be deformed elastically by the rolls to the same flattenedconfiguration as the surrounding regions. Because the deformation iselastic rather than plastic the stresses built up at each irregularityare not dispersed by permanent deformations of the surrounding regions.The material is immediately wound tightly in this flattened conditionand is thereafter maintained in its flattened condition by the winding.The resulting packaged product is thus free from surface defects andfrom entrapped air pockets.

According to another aspect the present invention involves the provisionof a frame containing an internally heated drum, a back nip roll and acrush roll. The back nip and crush rolls press against the heated drumat displaced locations to enable sheet material to be held against thesurface of the drum while passing over it. The frame is arranged to beactuated in a manner such that the crush roll is pressed tightly againsta drawings, illustrating by way of example a preferred form of theinvention.

In the drawings:

FIG. 1 is a perspective view, partially diagrammatic, illustrating asheet packaging arrangement according to the present invention; and

FIG. 2 is an enlarged fragmentary cross section taken along line 2-2 ofFIG. 1.

As shown in the drawings a web 10 of plastic sheet material, such aspolyvinyl chloride, is supplied continuously from a sheet-formingstation and a dancer roll tension device (not shown), and it passesthrough the nip of a back nip roll 12 and a heated drum 14. The web 10continues around the outer surface of the drum l4 and between the nip ofa crush roll 16 and the drum. Beyond this nip the web 10 remains inintimate contact with the outer surface of the crush roll 16 and passesthrough the nip of a takeup roll 18 and the crush roll 16. The web iswound up on the takeup roll 18.

As indicated schematically in FIG. 1, the back nip roll 12, the heateddrum 14 and the crush roll 16 are mounted on a common frame 20 so thatthese rolls press tightly against each other. The frame 20 in turn ispivotally mounted, as indicated at 22 so that the crush roll 16 may moveagainst and away from the takeup roll 18. This allows the system toaccommodate the effectively increasing diameter of the takeup roll 18 asmore and more of the web 10 is wound thereon.

Nip pressure between the crush roll 16 and the takeup roll 18 isobtained by means of a fluid actuator 24 which forces the pivotallymounted frame 20 in the direction of the takeup roll. Nip pressure canalso be controlled by adjustment of the pressure in the actuator 24.

The heated drum 14, as shown in FIG. 2, comprises an outer surfaceportion 26 and an inner fluid-containing portion 28. Heating fluid 30such as steam or hot water, fills the inner portion 28. As shown in FIG.1 the heating fluid is circulated through the drum 14 by means of apiping system 32 and a pump 34. A heater 36 is also provided along theheating fluid circuit. The heater 36 is thermostatically controlled tomaintain the temperature of the water passing through it. With thisarrangement the drum 14 may be rotatedcontinuously while a uniformtemperature is maintained about its outer surface.

The crush roll 16 comprises a steel core 38 covered with a hard rubber(e.g. 70-80 durometer neoprene) cover 40, approximately 0.5-inch thick.The diameter of the crush roll 16 is considerably smaller than that ofthe drum. For example, the drum diameter may be approximately 12 incheswhile the crush roll diameter may be about 3Vzinches.

In operation of the above described device, the web 10 passes over theback nip roll 12, around a sector of the heated drum l4 and over thecrush roll 16. The back nip and crush rolls 12 and 16 hold the web 10tightly against the surface of the drum over a sector of about The drumheats the web 10 uniformly during this time and brings it to atemperature where the web exhibits substantial elastomeric properties.The web 10 as thus heated is carried tightly around over the uppersurface of the crush roll and is then pressed against the takeup roll 18as it is being wound up thereon.

The heating of the web 10 by the drum 14 brings it to an elastomericcondition so that the pressure applied by the crush roll 16 will actupon any surface irregularities in the sheet and return them to aflattened condition without producing any plastic deformation whichresults in undesirable thickness or caliper changes. It will beappreciated that the longitudinal tension in the web 10 is kept belowthat in which caliper or thickness will change due to plasticdeformation.

The heated drum 14 is of rather large diameter in order to providesufficient drum surface area to bring the web 10 up to temperature in asmooth uniform manner. This large diameter, however, does not permit thedrum to exert high nip pressures. On the other hand, the small diametercrush roll 16, having a sharp curvature, concentrates its appliedpressure against the takeup roll 18 more nearly in a line and thepressure in the nip of the crush and takeup rolls 16 and 18 can be madequite high. The small diameter of the crush roll 16 also serves tominimize the travel time of the web between the heated drum and the nipof the crush and takeup rolls. Consequently the web remains in itselastomeric state during the ironing action of the crush roll 16 andwinding action of the takeup roll 18. It will also be appreciated thatwith the heating drum 14, the crush roll 16 and the takeup roll 18 allin intimate contact at least one surface of the web 10 receives supportduring its entire travel through the packaging system. This serves toensure that undue stretching will not occur.

The present invention provides excellent results when used to packagepolyvinyl chloride clear calendered sheeting of 0.005-0.020 gauge andmedium hard. in one instance such sheeting was passed over the drum at alineal speed of 20-50 yards per minute while the drum was maintained ata temperature of 85-l 10 F. The pressure of the crush roll 16 againstthe takeup roll 18 was made sufficient to flatten all observabledeformations in the sheet. The resulting packaged winding wascharacterized by an absence of imperfections caused by air pockets andit presented a high quality completely blue appearance.

It will be appreciated that the principles of the present invention areapplicable to all sheet materials which are elastomeric or which exhibitsubstantial elastomeric properties within certain temperature ranges.However, especially good results are obtained with elastomeric vinylhalide polymer compositions. These compositions may be defined ascontaining vinyl halide homopolymers or copolymers plasticizers,stabilizers, and the other additives that are commonly used in this typeof composition, The useful polymers include, for example, polyvinylchloride, polyvinylidene chloride, and vinyl chloride copolymers withvinyl acetate, vinyl butyrate, vinylidene chloride, styrene, methylmethacrylate, dialkyl fumarates, dialkyl maleates, etc.

What is claimed and desired to be secured by Letters Patent is:

1 Apparatus for packaging a web of sheet material, said apparatuscomprising means for heating said web, ironing means for applyingflattening pressure to both sides of the so-heated web, and means forwinding the so-i'lattened, heated web into a dense package, said heatingmeans and ironing means being mounted so as to press against each otherand said winding means being pressed against said ironing means,

2. Apparatus according to claim 1 wherein said heating means comprises aheated drum, said ironing means comprises a crush roll, and said meansfor winding comprises a takeup roll.

3. Apparatus according to claim 2 wherein said heated drum and crushroll are mounted on a common frame so as to press against each other andsaid takeup roll is mounted so as to press against said crush roll.

4. Apparatus according to claim 3 wherein said frame is mounted formovement against said takeup roll and an actuator means causes saidcrush roll to press against said takeup roll.

5. The method for the packaging of a web of thermoplastic sheet materialthat comprises the steps of heating said web, ironing said web byapplying a flattening pressure to both sides of the so-heated web, andwinding the so-flattened web into a dense package, the pressure that isapplied to both sides of the heated web being maintained during theheating and winding steps 6. The method of claim 5 wherein the web ispassed successively over a heated drum, a crush roll, and a takeup rollwhile said rolls press against each other.

1. Apparatus for packaging a web of sheet material, said apparatuscomprising means for heating said web, ironing means for applyingflattening pressure to both sides of the so-heaTed web, and means forwinding the so-flattened, heated web into a dense package, said heatingmeans and ironing means being mounted so as to press against each otherand said winding means being pressed against said ironing means. 2.Apparatus according to claim 1 wherein said heating means comprises aheated drum, said ironing means comprises a crush roll, and said meansfor winding comprises a takeup roll.
 3. Apparatus according to claim 2wherein said heated drum and crush roll are mounted on a common frame soas to press against each other and said takeup roll is mounted so as topress against said crush roll.
 4. Apparatus according to claim 3 whereinsaid frame is mounted for movement against said takeup roll and anactuator means causes said crush roll to press against said takeup roll.5. The method for the packaging of a web of thermoplastic sheet materialthat comprises the steps of heating said web, ironing said web byapplying a flattening pressure to both sides of the so-heated web, andwinding the so-flattened web into a dense package, the pressure that isapplied to both sides of the heated web being maintained during theheating and winding steps.
 6. The method of claim 5 wherein the web ispassed successively over a heated drum, a crush roll, and a takeup rollwhile said rolls press against each other.